644402690 has 8 divisors (see below), whose sum is σ = 1159924860. Its totient is φ = 257761072.

The previous prime is 644402623. The next prime is 644402713. The reversal of 644402690 is 96204446.

It can be written as a sum of positive squares in 2 ways, for example, as 611028961 + 33373729 = 24719^2 + 5777^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×644402690² = 830509653758472200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 644402690.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32220125 + ... + 32220144.

Almost surely, 2^644402690 is an apocalyptic number.

644402690 is a deficient number, since it is larger than the sum of its proper divisors (515522170).

644402690 is a wasteful number, since it uses less digits than its factorization.

644402690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64440276.

The product of its (nonzero) digits is 41472, while the sum is 35.

The square root of 644402690 is about 25385.0879454848. The cubic root of 644402690 is about 863.7454677540.

The spelling of 644402690 in words is "six hundred forty-four million, four hundred two thousand, six hundred ninety".